Expanding Family of Litharge-Derived Sulfate Minerals and Synthetic Compounds: Preparation and Crystal Structures of [Bi₂CuO₃]SO₄ and [<i>Ln</i>₂O₂]SO₄ (<i>Ln</i> = Dy and Ho)

• Main Authors: Oleg Siidra, Dmitri Charkin, Igor Plokhikh, Evgeny Nazarchuk, Astrid Holzheid, Georgy Akimov
• Format: Article
• Language: English
• Published: MDPI AG 2020-10-01
• Series: Minerals
• Subjects: sulfates; litharge; layered structures; copper; lanthanides; crystal structure
• Online Access: https://www.mdpi.com/2075-163X/10/10/887
• ISSN: 2075-163X

During the last decades, layered structures have attracted particular and increasing interest due to the multitude of outstanding properties exhibited by their representatives. Particularly common among their archetypes, with a significant number of mineral and synthetic species structural derivatives, is that of litharge. In the current paper, we report the structural studies of two later rare-earth oxysulfates, [<i>Ln</i>₂O₂]SO₄ (<i>Ln</i> = Dy, Ho), which belong indeed to the grandreefite family, and a novel compound [Bi₂CuO₃]SO₄, which belongs to a new structure type and demonstrates the second example of Cu²⁺ incorporation into litharge-type slabs. Crystals of [Bi₂CuO₃]SO₄ were obtained under high-pressure/high-temperature (HP/HT) conditions, whereas polycrystalline samples of [<i>Ln</i>₂O₂]SO₄ (<i>Ln</i> = Dy, Ho) compounds were prepared via an exchange solid-state reaction. The crystal structure of [Bi₂CuO₃]SO₄ is based on alternation of continuous [Bi₂CuO₃]²⁺ layers of edge-sharing OBi₂Cu₂ and OBi₃Cu tetrahedra and sheets of sulfate groups. Cu²⁺ cations are in <i>cis</i> position in O5Bi₂Cu₂ and O6Bi₂Cu₂ oxocentered tetrahedra in litharge slab. The crystal structure of [<i>Ln</i>₂O₂]SO₄ (<i>Ln</i> = Dy, Ho) is completely analogous to those of grandreefite and oxysulfates of La, Sm, Eu, and Bi.